1/*-
2 * Copyright (c) 2014 John Baldwin
3 * Copyright (c) 2014, 2016 The FreeBSD Foundation
4 *
5 * Portions of this software were developed by Konstantin Belousov
6 * under sponsorship from the FreeBSD Foundation.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD: stable/11/sys/kern/kern_procctl.c 352125 2019-09-10 07:29:21Z kib $");
32
33#include <sys/param.h>
34#include <sys/systm.h>
35#include <sys/capsicum.h>
36#include <sys/lock.h>
37#include <sys/mutex.h>
38#include <sys/priv.h>
39#include <sys/proc.h>
40#include <sys/procctl.h>
41#include <sys/sx.h>
42#include <sys/syscallsubr.h>
43#include <sys/sysproto.h>
44#include <sys/wait.h>
45
46static int
47protect_setchild(struct thread *td, struct proc *p, int flags)
48{
49
50	PROC_LOCK_ASSERT(p, MA_OWNED);
51	if (p->p_flag & P_SYSTEM || p_cansched(td, p) != 0)
52		return (0);
53	if (flags & PPROT_SET) {
54		p->p_flag |= P_PROTECTED;
55		if (flags & PPROT_INHERIT)
56			p->p_flag2 |= P2_INHERIT_PROTECTED;
57	} else {
58		p->p_flag &= ~P_PROTECTED;
59		p->p_flag2 &= ~P2_INHERIT_PROTECTED;
60	}
61	return (1);
62}
63
64static int
65protect_setchildren(struct thread *td, struct proc *top, int flags)
66{
67	struct proc *p;
68	int ret;
69
70	p = top;
71	ret = 0;
72	sx_assert(&proctree_lock, SX_LOCKED);
73	for (;;) {
74		ret |= protect_setchild(td, p, flags);
75		PROC_UNLOCK(p);
76		/*
77		 * If this process has children, descend to them next,
78		 * otherwise do any siblings, and if done with this level,
79		 * follow back up the tree (but not past top).
80		 */
81		if (!LIST_EMPTY(&p->p_children))
82			p = LIST_FIRST(&p->p_children);
83		else for (;;) {
84			if (p == top) {
85				PROC_LOCK(p);
86				return (ret);
87			}
88			if (LIST_NEXT(p, p_sibling)) {
89				p = LIST_NEXT(p, p_sibling);
90				break;
91			}
92			p = p->p_pptr;
93		}
94		PROC_LOCK(p);
95	}
96}
97
98static int
99protect_set(struct thread *td, struct proc *p, int flags)
100{
101	int error, ret;
102
103	switch (PPROT_OP(flags)) {
104	case PPROT_SET:
105	case PPROT_CLEAR:
106		break;
107	default:
108		return (EINVAL);
109	}
110
111	if ((PPROT_FLAGS(flags) & ~(PPROT_DESCEND | PPROT_INHERIT)) != 0)
112		return (EINVAL);
113
114	error = priv_check(td, PRIV_VM_MADV_PROTECT);
115	if (error)
116		return (error);
117
118	if (flags & PPROT_DESCEND)
119		ret = protect_setchildren(td, p, flags);
120	else
121		ret = protect_setchild(td, p, flags);
122	if (ret == 0)
123		return (EPERM);
124	return (0);
125}
126
127static int
128reap_acquire(struct thread *td, struct proc *p)
129{
130
131	sx_assert(&proctree_lock, SX_XLOCKED);
132	if (p != curproc)
133		return (EPERM);
134	if ((p->p_treeflag & P_TREE_REAPER) != 0)
135		return (EBUSY);
136	p->p_treeflag |= P_TREE_REAPER;
137	/*
138	 * We do not reattach existing children and the whole tree
139	 * under them to us, since p->p_reaper already seen them.
140	 */
141	return (0);
142}
143
144static int
145reap_release(struct thread *td, struct proc *p)
146{
147
148	sx_assert(&proctree_lock, SX_XLOCKED);
149	if (p != curproc)
150		return (EPERM);
151	if (p == initproc)
152		return (EINVAL);
153	if ((p->p_treeflag & P_TREE_REAPER) == 0)
154		return (EINVAL);
155	reaper_abandon_children(p, false);
156	return (0);
157}
158
159static int
160reap_status(struct thread *td, struct proc *p,
161    struct procctl_reaper_status *rs)
162{
163	struct proc *reap, *p2, *first_p;
164
165	sx_assert(&proctree_lock, SX_LOCKED);
166	bzero(rs, sizeof(*rs));
167	if ((p->p_treeflag & P_TREE_REAPER) == 0) {
168		reap = p->p_reaper;
169	} else {
170		reap = p;
171		rs->rs_flags |= REAPER_STATUS_OWNED;
172	}
173	if (reap == initproc)
174		rs->rs_flags |= REAPER_STATUS_REALINIT;
175	rs->rs_reaper = reap->p_pid;
176	rs->rs_descendants = 0;
177	rs->rs_children = 0;
178	if (!LIST_EMPTY(&reap->p_reaplist)) {
179		first_p = LIST_FIRST(&reap->p_children);
180		if (first_p == NULL)
181			first_p = LIST_FIRST(&reap->p_reaplist);
182		rs->rs_pid = first_p->p_pid;
183		LIST_FOREACH(p2, &reap->p_reaplist, p_reapsibling) {
184			if (proc_realparent(p2) == reap)
185				rs->rs_children++;
186			rs->rs_descendants++;
187		}
188	} else {
189		rs->rs_pid = -1;
190	}
191	return (0);
192}
193
194static int
195reap_getpids(struct thread *td, struct proc *p, struct procctl_reaper_pids *rp)
196{
197	struct proc *reap, *p2;
198	struct procctl_reaper_pidinfo *pi, *pip;
199	u_int i, n;
200	int error;
201
202	sx_assert(&proctree_lock, SX_LOCKED);
203	PROC_UNLOCK(p);
204	reap = (p->p_treeflag & P_TREE_REAPER) == 0 ? p->p_reaper : p;
205	n = i = 0;
206	error = 0;
207	LIST_FOREACH(p2, &reap->p_reaplist, p_reapsibling)
208		n++;
209	sx_unlock(&proctree_lock);
210	if (rp->rp_count < n)
211		n = rp->rp_count;
212	pi = malloc(n * sizeof(*pi), M_TEMP, M_WAITOK);
213	sx_slock(&proctree_lock);
214	LIST_FOREACH(p2, &reap->p_reaplist, p_reapsibling) {
215		if (i == n)
216			break;
217		pip = &pi[i];
218		bzero(pip, sizeof(*pip));
219		pip->pi_pid = p2->p_pid;
220		pip->pi_subtree = p2->p_reapsubtree;
221		pip->pi_flags = REAPER_PIDINFO_VALID;
222		if (proc_realparent(p2) == reap)
223			pip->pi_flags |= REAPER_PIDINFO_CHILD;
224		if ((p2->p_treeflag & P_TREE_REAPER) != 0)
225			pip->pi_flags |= REAPER_PIDINFO_REAPER;
226		i++;
227	}
228	sx_sunlock(&proctree_lock);
229	error = copyout(pi, rp->rp_pids, i * sizeof(*pi));
230	free(pi, M_TEMP);
231	sx_slock(&proctree_lock);
232	PROC_LOCK(p);
233	return (error);
234}
235
236static void
237reap_kill_proc(struct thread *td, struct proc *p2, ksiginfo_t *ksi,
238    struct procctl_reaper_kill *rk, int *error)
239{
240	int error1;
241
242	PROC_LOCK(p2);
243	error1 = p_cansignal(td, p2, rk->rk_sig);
244	if (error1 == 0) {
245		pksignal(p2, rk->rk_sig, ksi);
246		rk->rk_killed++;
247		*error = error1;
248	} else if (*error == ESRCH) {
249		rk->rk_fpid = p2->p_pid;
250		*error = error1;
251	}
252	PROC_UNLOCK(p2);
253}
254
255struct reap_kill_tracker {
256	struct proc *parent;
257	TAILQ_ENTRY(reap_kill_tracker) link;
258};
259
260TAILQ_HEAD(reap_kill_tracker_head, reap_kill_tracker);
261
262static void
263reap_kill_sched(struct reap_kill_tracker_head *tracker, struct proc *p2)
264{
265	struct reap_kill_tracker *t;
266
267	t = malloc(sizeof(struct reap_kill_tracker), M_TEMP, M_WAITOK);
268	t->parent = p2;
269	TAILQ_INSERT_TAIL(tracker, t, link);
270}
271
272static int
273reap_kill(struct thread *td, struct proc *p, struct procctl_reaper_kill *rk)
274{
275	struct proc *reap, *p2;
276	ksiginfo_t ksi;
277	struct reap_kill_tracker_head tracker;
278	struct reap_kill_tracker *t;
279	int error;
280
281	sx_assert(&proctree_lock, SX_LOCKED);
282	if (IN_CAPABILITY_MODE(td))
283		return (ECAPMODE);
284	if (rk->rk_sig <= 0 || rk->rk_sig > _SIG_MAXSIG ||
285	    (rk->rk_flags & ~(REAPER_KILL_CHILDREN |
286	    REAPER_KILL_SUBTREE)) != 0 || (rk->rk_flags &
287	    (REAPER_KILL_CHILDREN | REAPER_KILL_SUBTREE)) ==
288	    (REAPER_KILL_CHILDREN | REAPER_KILL_SUBTREE))
289		return (EINVAL);
290	PROC_UNLOCK(p);
291	reap = (p->p_treeflag & P_TREE_REAPER) == 0 ? p->p_reaper : p;
292	ksiginfo_init(&ksi);
293	ksi.ksi_signo = rk->rk_sig;
294	ksi.ksi_code = SI_USER;
295	ksi.ksi_pid = td->td_proc->p_pid;
296	ksi.ksi_uid = td->td_ucred->cr_ruid;
297	error = ESRCH;
298	rk->rk_killed = 0;
299	rk->rk_fpid = -1;
300	if ((rk->rk_flags & REAPER_KILL_CHILDREN) != 0) {
301		for (p2 = LIST_FIRST(&reap->p_children); p2 != NULL;
302		    p2 = LIST_NEXT(p2, p_sibling)) {
303			reap_kill_proc(td, p2, &ksi, rk, &error);
304			/*
305			 * Do not end the loop on error, signal
306			 * everything we can.
307			 */
308		}
309	} else {
310		TAILQ_INIT(&tracker);
311		reap_kill_sched(&tracker, reap);
312		while ((t = TAILQ_FIRST(&tracker)) != NULL) {
313			MPASS((t->parent->p_treeflag & P_TREE_REAPER) != 0);
314			TAILQ_REMOVE(&tracker, t, link);
315			for (p2 = LIST_FIRST(&t->parent->p_reaplist); p2 != NULL;
316			    p2 = LIST_NEXT(p2, p_reapsibling)) {
317				if (t->parent == reap &&
318				    (rk->rk_flags & REAPER_KILL_SUBTREE) != 0 &&
319				    p2->p_reapsubtree != rk->rk_subtree)
320					continue;
321				if ((p2->p_treeflag & P_TREE_REAPER) != 0)
322					reap_kill_sched(&tracker, p2);
323				reap_kill_proc(td, p2, &ksi, rk, &error);
324			}
325			free(t, M_TEMP);
326		}
327	}
328	PROC_LOCK(p);
329	return (error);
330}
331
332static int
333trace_ctl(struct thread *td, struct proc *p, int state)
334{
335
336	PROC_LOCK_ASSERT(p, MA_OWNED);
337
338	/*
339	 * Ktrace changes p_traceflag from or to zero under the
340	 * process lock, so the test does not need to acquire ktrace
341	 * mutex.
342	 */
343	if ((p->p_flag & P_TRACED) != 0 || p->p_traceflag != 0)
344		return (EBUSY);
345
346	switch (state) {
347	case PROC_TRACE_CTL_ENABLE:
348		if (td->td_proc != p)
349			return (EPERM);
350		p->p_flag2 &= ~(P2_NOTRACE | P2_NOTRACE_EXEC);
351		break;
352	case PROC_TRACE_CTL_DISABLE_EXEC:
353		p->p_flag2 |= P2_NOTRACE_EXEC | P2_NOTRACE;
354		break;
355	case PROC_TRACE_CTL_DISABLE:
356		if ((p->p_flag2 & P2_NOTRACE_EXEC) != 0) {
357			KASSERT((p->p_flag2 & P2_NOTRACE) != 0,
358			    ("dandling P2_NOTRACE_EXEC"));
359			if (td->td_proc != p)
360				return (EPERM);
361			p->p_flag2 &= ~P2_NOTRACE_EXEC;
362		} else {
363			p->p_flag2 |= P2_NOTRACE;
364		}
365		break;
366	default:
367		return (EINVAL);
368	}
369	return (0);
370}
371
372static int
373trace_status(struct thread *td, struct proc *p, int *data)
374{
375
376	if ((p->p_flag2 & P2_NOTRACE) != 0) {
377		KASSERT((p->p_flag & P_TRACED) == 0,
378		    ("%d traced but tracing disabled", p->p_pid));
379		*data = -1;
380	} else if ((p->p_flag & P_TRACED) != 0) {
381		*data = p->p_pptr->p_pid;
382	} else {
383		*data = 0;
384	}
385	return (0);
386}
387
388static int
389trapcap_ctl(struct thread *td, struct proc *p, int state)
390{
391
392	PROC_LOCK_ASSERT(p, MA_OWNED);
393
394	switch (state) {
395	case PROC_TRAPCAP_CTL_ENABLE:
396		p->p_flag2 |= P2_TRAPCAP;
397		break;
398	case PROC_TRAPCAP_CTL_DISABLE:
399		p->p_flag2 &= ~P2_TRAPCAP;
400		break;
401	default:
402		return (EINVAL);
403	}
404	return (0);
405}
406
407static int
408trapcap_status(struct thread *td, struct proc *p, int *data)
409{
410
411	*data = (p->p_flag2 & P2_TRAPCAP) != 0 ? PROC_TRAPCAP_CTL_ENABLE :
412	    PROC_TRAPCAP_CTL_DISABLE;
413	return (0);
414}
415
416static int
417stackgap_ctl(struct thread *td, struct proc *p, int state)
418{
419	PROC_LOCK_ASSERT(p, MA_OWNED);
420
421	if ((state & ~(PROC_STACKGAP_ENABLE | PROC_STACKGAP_DISABLE |
422	    PROC_STACKGAP_ENABLE_EXEC | PROC_STACKGAP_DISABLE_EXEC)) != 0)
423		return (EINVAL);
424	switch (state & (PROC_STACKGAP_ENABLE | PROC_STACKGAP_DISABLE)) {
425	case PROC_STACKGAP_ENABLE:
426		if ((p->p_flag2 & P2_STKGAP_DISABLE) != 0)
427			return (EINVAL);
428		break;
429	case PROC_STACKGAP_DISABLE:
430		p->p_flag2 |= P2_STKGAP_DISABLE;
431		break;
432	case 0:
433		break;
434	default:
435		return (EINVAL);
436	}
437	switch (state & (PROC_STACKGAP_ENABLE_EXEC |
438	    PROC_STACKGAP_DISABLE_EXEC)) {
439	case PROC_STACKGAP_ENABLE_EXEC:
440		p->p_flag2 &= ~P2_STKGAP_DISABLE_EXEC;
441		break;
442	case PROC_STACKGAP_DISABLE_EXEC:
443		p->p_flag2 |= P2_STKGAP_DISABLE_EXEC;
444		break;
445	case 0:
446		break;
447	default:
448		return (EINVAL);
449	}
450	return (0);
451}
452
453static int
454stackgap_status(struct thread *td, struct proc *p, int *data)
455{
456	PROC_LOCK_ASSERT(p, MA_OWNED);
457
458	*data = (p->p_flag2 & P2_STKGAP_DISABLE) != 0 ? PROC_STACKGAP_DISABLE :
459	    PROC_STACKGAP_ENABLE;
460	*data |= (p->p_flag2 & P2_STKGAP_DISABLE_EXEC) != 0 ?
461	    PROC_STACKGAP_DISABLE_EXEC : PROC_STACKGAP_ENABLE_EXEC;
462	return (0);
463}
464
465#ifndef _SYS_SYSPROTO_H_
466struct procctl_args {
467	idtype_t idtype;
468	id_t	id;
469	int	com;
470	void	*data;
471};
472#endif
473/* ARGSUSED */
474int
475sys_procctl(struct thread *td, struct procctl_args *uap)
476{
477	void *data;
478	union {
479		struct procctl_reaper_status rs;
480		struct procctl_reaper_pids rp;
481		struct procctl_reaper_kill rk;
482	} x;
483	int error, error1, flags, signum;
484
485	switch (uap->com) {
486	case PROC_SPROTECT:
487	case PROC_STACKGAP_CTL:
488	case PROC_TRACE_CTL:
489	case PROC_TRAPCAP_CTL:
490		error = copyin(uap->data, &flags, sizeof(flags));
491		if (error != 0)
492			return (error);
493		data = &flags;
494		break;
495	case PROC_REAP_ACQUIRE:
496	case PROC_REAP_RELEASE:
497		if (uap->data != NULL)
498			return (EINVAL);
499		data = NULL;
500		break;
501	case PROC_REAP_STATUS:
502		data = &x.rs;
503		break;
504	case PROC_REAP_GETPIDS:
505		error = copyin(uap->data, &x.rp, sizeof(x.rp));
506		if (error != 0)
507			return (error);
508		data = &x.rp;
509		break;
510	case PROC_REAP_KILL:
511		error = copyin(uap->data, &x.rk, sizeof(x.rk));
512		if (error != 0)
513			return (error);
514		data = &x.rk;
515		break;
516	case PROC_STACKGAP_STATUS:
517	case PROC_TRACE_STATUS:
518	case PROC_TRAPCAP_STATUS:
519		data = &flags;
520		break;
521	case PROC_PDEATHSIG_CTL:
522		error = copyin(uap->data, &signum, sizeof(signum));
523		if (error != 0)
524			return (error);
525		data = &signum;
526		break;
527	case PROC_PDEATHSIG_STATUS:
528		data = &signum;
529		break;
530	default:
531		return (EINVAL);
532	}
533	error = kern_procctl(td, uap->idtype, uap->id, uap->com, data);
534	switch (uap->com) {
535	case PROC_REAP_STATUS:
536		if (error == 0)
537			error = copyout(&x.rs, uap->data, sizeof(x.rs));
538		break;
539	case PROC_REAP_KILL:
540		error1 = copyout(&x.rk, uap->data, sizeof(x.rk));
541		if (error == 0)
542			error = error1;
543		break;
544	case PROC_STACKGAP_STATUS:
545	case PROC_TRACE_STATUS:
546	case PROC_TRAPCAP_STATUS:
547		if (error == 0)
548			error = copyout(&flags, uap->data, sizeof(flags));
549		break;
550	case PROC_PDEATHSIG_STATUS:
551		if (error == 0)
552			error = copyout(&signum, uap->data, sizeof(signum));
553		break;
554	}
555	return (error);
556}
557
558static int
559kern_procctl_single(struct thread *td, struct proc *p, int com, void *data)
560{
561
562	PROC_LOCK_ASSERT(p, MA_OWNED);
563	switch (com) {
564	case PROC_SPROTECT:
565		return (protect_set(td, p, *(int *)data));
566	case PROC_STACKGAP_CTL:
567		return (stackgap_ctl(td, p, *(int *)data));
568	case PROC_STACKGAP_STATUS:
569		return (stackgap_status(td, p, data));
570	case PROC_REAP_ACQUIRE:
571		return (reap_acquire(td, p));
572	case PROC_REAP_RELEASE:
573		return (reap_release(td, p));
574	case PROC_REAP_STATUS:
575		return (reap_status(td, p, data));
576	case PROC_REAP_GETPIDS:
577		return (reap_getpids(td, p, data));
578	case PROC_REAP_KILL:
579		return (reap_kill(td, p, data));
580	case PROC_TRACE_CTL:
581		return (trace_ctl(td, p, *(int *)data));
582	case PROC_TRACE_STATUS:
583		return (trace_status(td, p, data));
584	case PROC_TRAPCAP_CTL:
585		return (trapcap_ctl(td, p, *(int *)data));
586	case PROC_TRAPCAP_STATUS:
587		return (trapcap_status(td, p, data));
588	default:
589		return (EINVAL);
590	}
591}
592
593int
594kern_procctl(struct thread *td, idtype_t idtype, id_t id, int com, void *data)
595{
596	struct pgrp *pg;
597	struct proc *p;
598	int error, first_error, ok;
599	int signum;
600	bool tree_locked;
601
602	switch (com) {
603	case PROC_REAP_ACQUIRE:
604	case PROC_REAP_RELEASE:
605	case PROC_REAP_STATUS:
606	case PROC_REAP_GETPIDS:
607	case PROC_REAP_KILL:
608	case PROC_STACKGAP_CTL:
609	case PROC_STACKGAP_STATUS:
610	case PROC_TRACE_STATUS:
611	case PROC_TRAPCAP_STATUS:
612	case PROC_PDEATHSIG_CTL:
613	case PROC_PDEATHSIG_STATUS:
614		if (idtype != P_PID)
615			return (EINVAL);
616	}
617
618	switch (com) {
619	case PROC_PDEATHSIG_CTL:
620		signum = *(int *)data;
621		p = td->td_proc;
622		if ((id != 0 && id != p->p_pid) ||
623		    (signum != 0 && !_SIG_VALID(signum)))
624			return (EINVAL);
625		PROC_LOCK(p);
626		p->p_pdeathsig = signum;
627		PROC_UNLOCK(p);
628		return (0);
629	case PROC_PDEATHSIG_STATUS:
630		p = td->td_proc;
631		if (id != 0 && id != p->p_pid)
632			return (EINVAL);
633		PROC_LOCK(p);
634		*(int *)data = p->p_pdeathsig;
635		PROC_UNLOCK(p);
636		return (0);
637	}
638
639	switch (com) {
640	case PROC_SPROTECT:
641	case PROC_REAP_STATUS:
642	case PROC_REAP_GETPIDS:
643	case PROC_REAP_KILL:
644	case PROC_TRACE_CTL:
645	case PROC_TRAPCAP_CTL:
646		sx_slock(&proctree_lock);
647		tree_locked = true;
648		break;
649	case PROC_REAP_ACQUIRE:
650	case PROC_REAP_RELEASE:
651		sx_xlock(&proctree_lock);
652		tree_locked = true;
653		break;
654	case PROC_STACKGAP_CTL:
655	case PROC_STACKGAP_STATUS:
656	case PROC_TRACE_STATUS:
657	case PROC_TRAPCAP_STATUS:
658		tree_locked = false;
659		break;
660	default:
661		return (EINVAL);
662	}
663
664	switch (idtype) {
665	case P_PID:
666		p = pfind(id);
667		if (p == NULL) {
668			error = ESRCH;
669			break;
670		}
671		error = p_cansee(td, p);
672		if (error == 0)
673			error = kern_procctl_single(td, p, com, data);
674		PROC_UNLOCK(p);
675		break;
676	case P_PGID:
677		/*
678		 * Attempt to apply the operation to all members of the
679		 * group.  Ignore processes in the group that can't be
680		 * seen.  Ignore errors so long as at least one process is
681		 * able to complete the request successfully.
682		 */
683		pg = pgfind(id);
684		if (pg == NULL) {
685			error = ESRCH;
686			break;
687		}
688		PGRP_UNLOCK(pg);
689		ok = 0;
690		first_error = 0;
691		LIST_FOREACH(p, &pg->pg_members, p_pglist) {
692			PROC_LOCK(p);
693			if (p->p_state == PRS_NEW || p_cansee(td, p) != 0) {
694				PROC_UNLOCK(p);
695				continue;
696			}
697			error = kern_procctl_single(td, p, com, data);
698			PROC_UNLOCK(p);
699			if (error == 0)
700				ok = 1;
701			else if (first_error == 0)
702				first_error = error;
703		}
704		if (ok)
705			error = 0;
706		else if (first_error != 0)
707			error = first_error;
708		else
709			/*
710			 * Was not able to see any processes in the
711			 * process group.
712			 */
713			error = ESRCH;
714		break;
715	default:
716		error = EINVAL;
717		break;
718	}
719	if (tree_locked)
720		sx_unlock(&proctree_lock);
721	return (error);
722}
723